[11608] in cryptography@c2.net mail archive
Re: Quantum computers inch closer?
daemon@ATHENA.MIT.EDU (Jaap-Henk Hoepman)
Tue Sep 3 10:40:12 2002
To: cryptography@wasabisystems.com
In-Reply-To: <3D73DF30.DD119F1B@monmouth.com>
From: Jaap-Henk Hoepman <jhh@cs.kun.nl>
Date: 03 Sep 2002 10:10:33 +0200
On Mon, 02 Sep 2002 17:59:12 -0400 "John S. Denker" <jsd@monmouth.com> writes:
> The same applies even more strongly to quantum computing:
> It would be nice if you could take a classical circuit,
> automatically convert it to "the" corresponding quantum
> circuit, with the property that when presented with a
> superposition of questions it would produce "the"
> corresponding superposition of answers. But that cannot
> be. For starters, there will be some phase relationships
> between the various components of the superposition of
> answers, and the classical circuit provides no guidance
> as to what the phase relationships should be.
In fact you can! For any efficient classical circuit f there exists an
efficient quantum circuit Uf that does exactly what you describe:
when given an equal superposition of inputs it will produce the equal
superposition of corresponding outputs.
Jaap-Henk
--
Jaap-Henk Hoepman | Come sail your ships around me
Dept. of Computer Science | And burn your bridges down
University of Nijmegen | Nick Cave - "Ship Song"
Email: jhh@cs.kun.nl === WWW: www.cs.kun.nl/~jhh
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